1. Field of the Invention
The present invention relates to a semiconductor light-emitting device, and more particularly, to a semiconductor light-emitting device in which a light-emitting region provided on a surface of light-extraction side of the device has an annular shape.
2. Description of Related Art
FIGS. 8 and 9 are a plan view and sectional view of a conventional semiconductor light-emitting device, respectively. FIG. 10 is an explanatory view illustrating a light-emitting state of the conventional semiconductor light-emitting device (see, for example, Japanese Unexamined Patent Publication No. HEI 4(1992)-229665).
In FIGS. 8 to 10, a semiconductor light-emitting device 21 includes: a substrate 23 having an electrode 22 formed on its rear surface, and a lower cladding layer 24a, an active layer 25, an upper cladding layer 24b, a current-spreading layer 29 and an electrode 30 formed in this order on the substrate 23. The lower cladding layer 24a, active layer 25 and upper cladding layer 24b constitute a light-emitting region layer (light-emitting layer) 26. The light-emitting device 21 further includes, in a central region of the current-spreading layer 29, a current-blocking layer 28 formed on the light-emitting region layer 26 side of the layer 29. The current-blocking layer 28 is formed at a position where it opposes the electrode 30 located on the current-spreading layer 29.
Current injected into the current-spreading layer 29 from the electrode 30 spreads to the periphery of the current-blocking layer 28 and is then introduced into the light-emitting region layer 26, so that a light-emitting region 27 emits light. This allows for light-emission in portions other than the portion directly underneath the electrode 30. Consequently, the generated light is not cut off by the electrode 30 and thus, improving the efficiency of the device.
FIGS. 11 and 12 are a plan view and sectional view of another conventional semiconductor light-emitting device, respectively. FIG. 13 is an explanatory view illustrating a light-emitting state of the conventional light-emitting device (see, for example, Japanese Unexamined Patent Publication No. HEI 11(1999)-26810).
In FIGS. 11 to 13, a semiconductor light-emitting device 41 includes: a substrate 43 having an electrode 42 formed on its rear surface, and a lower cladding layer 44a, an active layer 45, an upper cladding layer 44b, a current-spreading layer 49 and an electrode 50 formed in this order on the substrate 43. The lower cladding layer 44a, active layer 45 and upper cladding layer 44b constitute a light-emitting region layer (light-emitting layer) 46. The light-emitting device 41 further includes, in an outer region of the current-spreading layer 49, a current-blocking layer (current-narrowing layer) 48 formed on the light-emitting region layer 46 side of the layer 49. The electrode 50 has an opening in the center thereof and is formed at a position where it opposes the current-blocking layer 48.
Current injected into the current spreading layer 49 from the electrode 50 is concentrated in the middle of the layer 49 and is then introduced into the light-emitting region layer 46, so that a light-emitting region 47 emits light. Since the current is concentrated in the middle of the device, a higher current density is obtained in the middle of the device. As the current density increases, the percentage of current that recombines without emitting light decreases and thus, improving the luminous intensity.
With the structure shown in FIGS. 8 to 10, however, currents spread freely to portions other than the current-blocking layer 28, whereby the density of current decreases.
The structure shown in FIGS. 11 to 13 requires a wire-bonding area 51 to be provided in a corner of the device. The wire-bonding area 51 usually needs a diameter of about 90 μm, and this obstructs reduction in device size.